Pancreatic islets in monolayer culture will be studied by rapid microspectrofluorometry in conjunction with microelectrophoretic injection of metabolites and probes. The intercellular communication of islet cells will be evaluated by the cell-to-cell transfer of fluorescent tracers (e.g., after microinjection of fluorescein, 1, N-ethenoadenosin cyclic phosphate into an islet cell). The islet cells used in microfluorometry will be retrieved (using a diamond marker) for subsequent identification of alpha and beta cells by immunofluorescence. The cell-to-cell transfer of metabolites (e.g., glycolytic intermediates) will be followed via changes in blue NAD(P)H emission due to NAD(P) yields (reversibly) NAD(P)H transients. The ability of various glycolytic intermediates to elicit NAD(P) yields (reversibly) NAD(P)H flourescence transients in islet cells will be compared in terms of both dose and time kinetics to their known, or postulated secretory actions. The intercellular passage of metabolites can help to explain "recruiting", i.e. the concerted activity of beta cells, or the functional coordination of alpha and beta cells, suggested by ultrastructural evidence for gap juctions. The sensitivity and spectral resolution of the microspectrofluorometer may permit detection of changes in the intracellular localization, intensity and spectrum of chlorotetracycline fluorescence which might be correlated to possible Ca2 ion translocations involved in secretion-stimulus coupling. A versatile microscopic-optical design will be gradually tailored to the requirements of these studies to include: optimization of probe fluorescence by multioptional excitation from mercury arc (330, 366, 436nm), helium-cadmium laser (325nm) or xenon; phase contrast for precise identification of epithelioid endocrine cells clustered within islets; darkfield for tentative identification of alpha and beta cell granules in endocrine cells within cluster; reflection contrast microscopy, a new method for visualization of cell surface (e.g., dynamic changes associated with secretory activity) and microcinematography.